Control of an excavation machine can be a difficult task to perform productively and efficiently, without causing operator fatigue. Such control can require years of experience and a high level of skill that not all operators possess. In order to improve performance of an excavation machine, even when controlled by inexperienced or low-skill operators, limitations on certain movements of the machine can be selectively implemented. For example, a limitation on the movement range of a machine tool can help prevent unnecessary movements into protected regions where undesired collisions and work delays could occur. In some situations, the limitations can be set by an operator of the machine based on a particular application and/or a desired work surface contour.
One example of an excavation system implementing selective movement limitation is disclosed in U.S. Pat. No. 5,968,104 (the '104 patent) issued to Egawa et al. on Oct. 19, 1999. In particular, the '104 patent discloses a hydraulic excavator having an area limiting excavation control system. The area limiting excavation control system comprises a setting device for providing an operator instruction to set an excavation area where an end of a bucket is allowed to move. The area limiting excavation control system also comprises angle sensors disposed at pivot points of a boom, an arm, and a bucket for detecting respective rotational angles and velocities thereof, a tilt angle sensor for detecting a tilt angle of the excavator's body in a back-and-forth direction (fore/aft direction), and a pressure sensor for detecting a load pressure of the boom as it is moved upward in response to signals generated by a control lever.
The area limiting excavation control system limits a speed of the bucket based on changing machine parameters. Specifically, as the bucket nears a boundary of the operator set excavation area during a fore/aft or up/down movement operation (i.e., during a digging operation), the speed of the bucket is slowed in the direction of the boundary such that the bucket stops at the boundary of the excavation area without exiting the excavation area. And, the stopping of the bucket is accurately and smoothly controlled by adapting flow rate characteristics of control valves associated with movement of the bucket for changing machine parameters such as speed, load, position, posture, and temperature.
Although the area limiting control system of the '104 patent may improve operator control and machine performance of a hydraulic excavator in a fore/aft direction, it may be limited. In particular, the system of the '104 patent may do little for control over a swinging of the excavator during a side-to-side movement operation (i.e., during a non-digging operation such as a swing-to-truck or a return-to-trench movement). In addition, the system of the '104 patent may not account for side-to-side tilting (i.e., rolling) of the excavator that can have a significant impact on the swinging velocities and forces of the excavator.
The disclosed control system is directed to overcoming one or more of the problems set forth above.